Circuit for generating sloping and rectangular gates



July 24, 1951 A. B. JAcoBsEN 2,561,475

cIRcuIT FOR GENERATING sLoPINc AND RECTANGULAR GATES Filed Nov. 28, 1945 DRECTIONAL ANTEN NA INVENTOR ANDREW B. .JAGOBSEN ATTORNEY tion of any desired target.v

Patented July 24, 1951 umrsojs'mrss FATF.

NT OFFICE X CIRCUIT FOR GENERATING SLOPI G AND` RECTANGULARGATES 1,, c 'Andrew B. Jaeobsen, somerviue, Mass., assignor, by mesne assignments, to the United States of America as represented by'the Secretary of the Navy Application November-72s, 1945,]seria1`No. 630,944

. This invention relates to methods and appara- `-tusfor generating sloping and rectangular gates, 1and more particularly, to methods and apparatus -for Vgenerating such gateswhose time of occur- `rence` cant-be controlled by a suitable external v,voltage c In a radar system for automatic tracking in range and azimuth=(orelevation) while the an- Ltenna performs a continuous 360 azimuth scan, vit is necessary to `-employ condenser storage or {Smemory devices." These memory devices are charged only during the time the radar beam illuminates the desired target, and for the re- 8 oiaims. (ci.` 2504-86) mainder of the azimuth scan they supply voltages ,1 i

Aproportional to the target position and movement. Inorder that these memory devices may be `clharged at the proper time, the input to these devicesmust be ugated, that is, no energy is :supplied to these devices except when the azimuth i of the radar antenna is such that the desired targietis illuminated. 'It is also necessary that the 'input tothe memory devices" be capable of self-correction.

j "In a known type of such a system, this selfv correction is made possible by using two sloping gates which have equalamplitudes at a point corresponding to the target azimuth. The input to the f'memory device in this system is gatedin azimuth by arectangular gate which is centered 'about a point corresponding to the target azimuth. Inthis known system, as the antenna rotates in azimuth, it generates, by linkage to a `rheostat orother means, a linear sawtooth which 'is` repeated once per revolution. This is a convenient source of basic sawtooth waveforms for the generation of-the necessary gates. but if this Jvoltage alone were used, the gates` would always appear at the same azimuth position. In any lautomatic tracking system,` however, it must be possible to position the gates at the azimuth posi- To do this is one object of my invention.

A more specific object of my invention is to rprovide an apparatus for generating a pair ofy sloping gates, one of the pair increasing in ampli- 'tude as the other decreases, and a rectangular "gate timed and Controlled by the pair of sloping gates.

` It is a further object of myinvention to provide an apparatus for generating such gates from a'basic sawtooth voltage, which gates are to be Fig. 12 'shows representative voltage waveforms at the input and output of my invention.

The embodiment of my invention shown in Fig. `1 is particularly adaptable to generating azimuth gates for a radar system employing automatic range and azimuth (or elevation) tracking. This i comprises a source, generally designated IO, of a series of linear sawtooth voltage waveforms, means Il for producing a pair of sloping gates, one increasing in `amplitude as the other decreases,,means 12 for controlling the time, or position relative to the' sawtooth voltage waveform, when the amplitude of one of the pair of sloping gates is equal to the other of the pair of sloping gates, and means 13 for producing, from the pair of sloping gates, a rectangular gate centered around the point of equal amplitudes of the pair of sloping gates.

The duration of the rectangular pulse is con`- trolled by a portion of the means I I, specifically, the resstors l4 and |5 and the grid 2| of the tube H.

Means ll for producing a pair of sloping gates comprises' a cathode coupled push-pull amplifier employing a pair of grid-controlled high-vacuum tubes IS and '11. Their cathodes 22 andl 23 are connected through a common resistor` 24- to ground. The anodes IB and |9 of tubes 16 and l'l are connected to a positive D..C. voltage through load resistors 25 and 26, respectively. The rectangular gate producing means 1|3 comprises a pair of switch tubes 21 and 28 having a common load resistor 29, and cathodes 30`and 3| connected together to a biasing means 32 and 33. Resistor 32 is connected on one side to a positive D. C. voltage and on the other side to a voltage regulator tube 33. The other side of tube 33 is connected to ground. v ``fLeads 34` and 35 couple the output of tubes IB jandil to Vcontrol grids 36 and 31 of tubes 21 and V28.' Lead 38 couples grid 20 of tube l`6 to the source I 2, of azimuth controlvoltage through a 'resistor 39, and to the source IO of the linear sawtooth voltage through a resistor 40. Resistors 39 and` lit)` are used to properly relatively propor- Ytion the two voltages supplied to the gridzll of tubel.

, The 'source IO of linearsawtooth voltage convsists of a directional antenna mechanically coupled, as indicated by dotted line 4|, to a rotatable arm 42 of 'an azimuth potentiometer 43. As ``the antenna rotates in azimuth, it generates, by linkage 'dl and arm 42 of potentiometer" 43,-'-*-`a linear sawtooth voltage waveform repeated once per revolution. This series of Voltage waveforins is`represented by curve a in Fig. 2.

IB increases, the potential at anode |8 decreases g U g I'ed' claims.

(see curve 41 in Fig. 2b). When it reaches .point 1 48 (see Fig. 2h), which corresponds to the cutoff grid potential of tube 21, current through resis-"' tor 29 quickly falls to zero, and terminal 44 rises f sharply in potential, producing the leading edgeA of the rectangular gate shown at e in Fig. 2.

As the sawtooth voltage input continues to rise`` z ternfto vgate the input to af'memoryudevice" of ;such a's'ystern. ,AThis g'atemay a1so belused for many other ipurposesg'for example; a variable w pedestal for supplying video energy to a cathode and more current is drawn through tube 16, the

potential of its cathode '22 rises and hence the bias onl tube l'l increases'. This is the usual cathode coupled push-pull effect, and current is decreased in tube'l'l. This causes the potential of itslan'ode `19 to rise, as shown by curve 49 in Fig. 2b.

` When anode 19, connected to grid 31 of tube 28 reaches point 50 (Fig. 2b), which corresponds to the cutoff grid potential of Vtube 28, tube 28 begins conduction, causing the potential at point :44 tov drop sharply, thereby producing the trailing edge of the rectangular gate (see e in Fig. 2). i When the sawtooth input drops, the initial conditions are re-established. As is apparent to a person skilled in the art, by raising the D. C`. level of grid 2| of tube I'l the rectangular gate width canbe increas'ed, and by lowering it the gate `width can be decreased.

From the above description, it is apparent that w lthe anode voltages of tubes IS and l'l generate the sloping gate voltages, while the anode volt- .I

age of tubes 21 and 28 generates the rectangular gate.

It will be understood that the D. C. level of grid .20 of tube 16 will control the time or position of Loccurrence of equal amplitudes of the sloping gates and hence, the time of the rectangular gate, relative to the sawtooth voltage input. These gates can therefore be made to occur at any posi- Jtiron of the antenna. o

.For example, assume the azimuth control voltage is increased in magnitude, the potential of lanode yi 8 of tube 16 will reach point 48 sooner (see Fig. 2a) than it would if the control voltage were less, and, therefore, the rectangular gate occurs nearer the minimum voltage point of the sawg, .tooth voltage (see Fig. 2)

In like manner, when the azimuth control voltage is decreased in magnitude the gates are as represented in Fig. 2d and Fig. 2g. Therefore, by controlling the D. C. level ofgrid 20 of tube |6 the point of equal amplitudes is; fof the pair of sloping gates and the rectangular 'gate can be located at any point relative to the lsawtooth voltage, and, therefore, to the antenna azimuth.

ACurve 41 in Figs. 2b, c and d represents the ,voltagewaveform atterminal 46 of Fig. l, and `lcu1've'49` in Figs. 2b, c and d represents the voltage waveform at terminal 45 of Fig. 1. The outputs available at th'ese two terminals may be used in combination with other circuits of an automatic range and azimuth tracking radar system to produce an error signal for azimuth tracking, thereby providing means of self-correction `Vin such a system. These sloping gates Vmay be used for other purposes, for example, sweep volt-v` tiff-ray indieator.

' This invention'islimited only by the append- Vamplifier employing. a pair of grid controlled high vacuum tubes, a pair of switch tubes employiigv a'o'mmon load resistor, the control grid of one of saidrpair of ampjlifier tubes beingcoupled 'to said sawtoothvoltage source and to said con- *trol'voltage' source,means connecting the control glridl of the' 'other offsaid pair of ampli'fierjtube's to 'afirst point of'fixed bias potential, means for v'coupling the control gridsiof'saidfpair of switch tubes to the output of said amplifierv tubes, and meansconnecting 'thec'cathode 'of 'each of'said 'switch tubes-to=a-second`1point of fixed'- bias' potential, whereby as said sawtooth voltage and vsaid controll voltage 'are' appliedgtosaid control grid of the firstv ofsaidpair 'of :amplifier'tubesfthere is produced at the 'output' of said `lamplifier tubes ajpair of' sloping flgates; o'ne increasing in amplitude as the other-decreases, said control Voltage 'determining the point; relative'to saicl'sawtooth voltage, of equal' amplitude of said pair of fsloping gates, 'and there isA prodiicd` atv the' output "of said pair'of'switch' tubesfa r'ectangular gate centered about saidv point 'of equalamplitudes of'said sloping g'ates,v the Vduration 'of said'r'ectangular gate being controlled by the biafs'of'` the second of said pair of arr'iplifiertub-is.v w

An apparatus forl generatinglsloping and rectangular .gates comprising, a Source of linear saw-tooth voltage Vsignals; 'an -adjustable' control voltage o source, va:cva'thocie coupledy amplifier in- .cluding firstand second'electron' tubes :having a common cathode impedance and individualanode ,impedances each of said electronltubes including a` controln grid, means vforV Vconnecting said control grid .of said. second electron tube 'o to `a ,point of fixed bias potential, .means couplingsaid ,source of saw-toothrsig'nals and vsaidcontrol voltgejsource to said ;ridf'ofsaid'first electron tube ;whereby theV signalsl,'ap'pearing'V across the anode irnpedance's of said, ,first andV second electron tubes, 'respectively, areapairf ofvsloping gates, one-of said vgatesMincreasing in amplitude as the other ofsaidgates .decreases ;in amplitude in predetermined phase relation to said saw-tooth voltage signals andwhereby adjustment of said control voltage source symmetricallyfvaries'the initialvalue of said twoogates .with 'respect to a value intermediate the initialV values of said' slopiing `gates;withoutaltering'the slope of said gates, ;third and fourth. electron tubes having'a common anode load impedance, each of' said last- `,mentioned two 1tubes being connected to pass currentA therethrough"l when 'the potential on a 'grid thereof exceeds 'a presele'cted value lying be- ,tweensaid initial values of saidgatfestmeans for lcoupling the signalf'a'ppeaicngfacrossV the anode Himpedance of said fir'st'electron tube'to' the grid I of said third electrontube and meansflforcoupling Athe signal appearing'a'cross 'the an'od'e vimpedance of' said second elect'r'on tube Vt'oitl'le "grid of said fourth elec'tron 'tube whreby'a' i'grial of predeterminedtime w'idthzsi'gnerfat 4 fcr'oss said'c'ommon anode impedance of said'th'ird'and fourth acer-475 electron tubes, said signal being movable in time position with respect to said saw-tooth signal by adjustment of said control voltage source.

3. An apparatus for generating sloping and rectangular gatesl comprising a source of linear saw-tooth voltage signals, a control voltage source, a cathode coupled amplifier including first and second electron tubes each having at least an anode, a cathode, and a control grid, a first load impedance connected. to said anode of said first electron tube, a second load impedance connected to said anode of said second electron tube, a common cathode impedance connected to said cathode of said first and second electron tubes, and means biasing said control grid of said second electron tube to a preselected fixed potential, means coupling said source of saw-tooth signals and said control Voltage source to said control grid of said first electron tube, a switch circuit comprising third and fourth electron tubes each having at least a cathode, an anode, and a control grid, a common anode load impedance connected to said anode of said third and fourth electron tubes, and means biasing said cathode of said third and fourth electron tubes at a preselected fixed potential, means coupling said anode of said first electron tube to said grid of said third electron tube, and means coupling said anode of said second electron tube to said grid of said fourth electron tube whereby, as said sawtooth voltage and said control voltage are applied to said control grid of said first electron tube, there is produced at the anode of said first and second electron tubes a pair of sloping gates, one gate increasing in amplitude as the other gate decreases in amplitude, said control voltage determining the point, relative to said saw-tooth voltage, of equal amplitude of said pair of sloping gates and whereby there is produced at the anode of said third and fourth electron tubes a rectangular gate centered about said point of equal amplitudes of said sloping gates.

4. A circuit for generating a gate adjustable in time relative to a linear saw-tooth voltage comprising means responsive to said saw-tooth voltage for producing a pair of sloping gates, one of said pair increasing in amplitude as the other of said pair decreases, voltage operated switch means adapted to pass current when a potential applied thereto exceeds a predetermined value, said predetermined value being higher than the amplitude of said gates when the amplitude of one of said gates equals the amplitude of the other of said gates, an impedance and a source of energy connected in series with said switch means and means separately connecting said pair of gates to said switch means, whereby current flows through said impedance during a preselected time interval centered about the time when said gates are equal in amplitude.

5. A circuit for generating a gate adjustable in time relative to a linear saw-tooth voltage comprising means responsive to said saw-tooth voltage for producing a series of pairs of sloping gates in predetermined time relation to said saw-tooth voltage, one of said pair increasing in amplitude as the other of said pair decreases, switch means responsive to said pair of gates, said switch means being adapted to permit the flow of current therethrough whenever the amplitude of either of said gates exceeds a preselected value and to interrupt the flow of current therethrough whenever the amplitude of both of said gates is below said preselected value, said preselectd value being selected so that said decreasing gate reaches said value prior to the time said increasing gate reaches said value, means for generating a gate when said switch means interrupts current therethrough, and means for adjusting the initial values of said sloping gates whereby the time at which said gates arrive at said preselected value is Variable in time with respect to said saw-tooth voltage.

6. A gate generator circuit comprising first and second electron tubes having a common anode load impedance, each of said electron tubes being adapted to pass current therethrough when the potential on a grid thereof exceeds a preselected value, means for generating a pair of sloping voltage gates, one of said gates increasing in amplitude as the other of said pair decreases in amplitude, said gates being so related that said decreasing gate reaches said preselected value prior to the time that said increasing gate reaches said value, means coupling said increasing gate to said grid of said first electron tube, and means coupling said decreasing gate to said grid of said second electron tube.

7. A gate generator circuit comprising first and second electron tubes having a common anode load impedance, each of said electron tubes being adapted to pass current therethrough when the potential on a grid thereof exceeds a preselected value, means for generating a pair of sloping voltage gates, one of said gates increasing in amplitude as the other of said pair decreases in amplitude, said gates being so related that said decreasing gate reaches said preselected value prior to the time that said increasing gate reaches said value, means coupling said increasing gate to said grid of said first electron tube, means coupling said decreasing gate to said grid of said second electron tube, and means for simultaneously varying with respect to the time of ini'tiation of said pair of gates the times at which said two gates reach said preselected value wherelby the time of occurrence of the gate generated by said circuit may be varied.

8. A gate generator circuit comprising first and second electron tubes having a common anode load impedance, each of said electron tubes being connected to pass current therethrough when the potential on a grid thereof exceeds a prselected value, means for generating a pair of sloping voltage gates, one of said gates increasing in amplitude as the other gate of said pair decreases in amplitude, said gates being so related that said decreasing gate reaches said preselected value prior to the time that said increasing gate reaches said value, means coupling said increasing gate to said control grid of said first electron tube, means coupling said decreasing gate to said grid of said second electron tube, and .means associated with said sloping gate generating means for varying the initial values of said gates symmetrically with respect to said preselected value whereby said time position of the signal appearing across said common anode impedance may be varied without altering the time width of said signal.

ANDREW B. JACOBSEN.

REFERENCES CI'I'ED UNITED STATES PATEN'I'S Name Date Campbell July 9. 1940 Number 

